The present invention relates to enhanced stabilization of co-rotating stacks of flexible record storage disks.
A co-rotating stack of record disks is generally stabilized by circumferentially uniform radially outwardly flowing air. Such stabilization is achieved either by self-ventilation characterized by apertured flexible record storage disks or by a separate pump for supplying air through a tubular spindle to interstices between the adjacent storage disks. It is also known that the access openings for transducer access is a function of the air flow and rotational speed of the record storage disk. Referring to FIG. 1, the ordinance represents a mass of air flow whereas the abscissa represents the rotational speed of the record storage disk. In prior analyses the mass flow shown in FIG. 1 was listed as a function of pressure in the tubular spindle. The operation of the stack of disks with pressure in accordance with the prior art includes an unstable area at extremely low pressure wherein the adjacent record storage disk could come into contact or take unpredictable axial relationships with each other. In a bistable region the disk could be side by side in parallel relationship or could be axially spaced apart similar to a transducer access opening. In fact, several storage apparatus employing a stack of co-rotating flexible storage disks are purposely pressured through the bistable range such that a mechanical or fluidic agitation of the disk can create a transducer access opening. Above the bistable range there is a stability range in which the co-rotating disks are generally always in parallel relationship. Above the stable range is a flutter range. It should be appreciated that the line separating the ranges are not point discontinuities but the whole range is a continuum of parameter changes.
It is desired to impart certain operational characteristics to such storage apparatus. Such operational characteristics require fast access openings and closings. To this end, the lower portion of the bistable range, i.e. adjacent the unstable range, is characterized by a rapid opening. However, it is plagued with slow closing. On the other hand, the upper end of the bistable range is characterized by fast closing and plagued by slow opening. Other parameters not pertinent to the understanding of the present invention affect flexible disk operations indicating that the range of operation of the stack of flexible disks should be restricted to a relatively narrow range of operation such that the design parameters of such record storage apparatus can be more readily achieved.
Such record storage apparatus operates under a wide variety of environmental conditions. For example, altitude changes as well as local weather pressure changes, also termed barometric changes, can have a substantial adverse or advantageous affect on disk stack operations. Further, temperature changes--particularly high temperature changes--tend to degrade disk stack operations. What is needed is a control mechanism and method for ensuring that the stack of co-rotating flexible storage disks are maintained in a narrow range of stabilizing operations.